The present invention relates to a magnetic disk apparatus, and more particularly, to a magnetic disk apparatus in which magnetic heads supported by a carriage assembly are connected to a control unit through a flexible printed circuit board.
In general, a magnetic disk apparatus comprises magnetic disks arranged in a casing, a spindle motor for supporting and rotating these disks, a carriage assembly that support magnetic heads, a voice coil motor for driving the carriage assembly, a substrate unit, etc.
The carriage assembly includes a bearing section attached to the casing and a plurality of arms extending from the bearing section. A magnetic head is mounted on each arm by means of a suspension. Signal wires for the magnetic heads are led along the arms to the bearing section, and are soldered one by one to one end portion of a main flexible printed circuit board (hereinafter referred to as main FPC). Alternatively, the signal wire for each magnetic head is connected to the main FPC through a junction FPC mounted on each corresponding arm. The other end portion of the main FPC is connected to the substrate unit. Thus, the magnetic heads are connected electrically to the substrate unit through the main FPC, and are controlled by means of the substrate unit.
Usually, the one end portion of the main FPC is fixed to the carriage assembly by a method (1) in which it is fixed by means of a screw that is screwed into an internal screw on the carriage assembly side through an aperture formed in the main FPC, a method (2) in which the one end portion is stuck on the carriage assembly with use of a double-coated adhesive tape or an adhesive, or a method (3) that combines those two methods.
With use of the method (1), a grounding conductor pattern formed on the main FPC can be easily grounded to the carriage assembly. In this case, however, an area for the connection of the magnetic head signal wires is narrowed by a margin equivalent to the area of the head of the fixing screw, and the magnetic head signal wires must be arranged without interfering with the screw head, so that the position for the connection and the like are restricted. In recent years, in particular, high-performance magnetic heads are frequently used with an increasing demand for higher recording density. According to this method, therefore, the magnetic heads require use of more signal wires, and this requirement cannot be fulfilled with ease.
With use of the method (2), on the other hand, there is a possibility of the main FPC separating from the carriage assembly, owing to change of temperature, vibrations, shocks, seek of the carriage assembly, etc. Thus, this method lacks in reliability.
It is difficult for the method (3), moreover, to solve the problems of the foregoing methods.